1. Field of the Invention
The present invention relates to glutaminase and a glutaminase gene encoding the same, more specifically, to a protein having a glutaminase activity and excellent in salt tolerance and thermostability, and a gene encoding the protein having a glutaminase activity.
2. Prior Art
Glutaminase is an enzyme which generates ammonia and L-glutamic acid which gives good taste by hydrolyzing L-glutamine. Glutaminase has an important role in a food industry and is useful for producing, for example, soy sauce or flavoring foods obtained by enzymatically hydrolyzing protein. Glutaminase has been isolated from various kinds of biological species and its enzymological properties and the gene have been reported (e.g., Japanese Patent Publication No. 38748/1994).
In the preparation of soy sauce and the preparation of flavoring foods containing a large amount of salt, glutaminase excellent in an optimum pH, salt tolerance and thermostability has been desired. A group to which the present inventors have belonged has previously found a novel glutaminase which is excellent in salt tolerance and thermostability, and can effectively produce a protein-hydrolyzed product (e.g., soy sauce) enriched in an amount of glutamic acid from Cryptococcus albidus ATCC20293 (Journal of Japan Soy Sauce Research Institute, Vol.13, No.5, 1987, pp. 205-210, herein incorporated by reference).
For further improving the property of the above enzyme by a genetic engineering means and for producing the enzyme in a large amount, it is important to obtain a gene of the enzyme.
According to the above, it is possible to improve qualities of the protein-hydrolyzed product (e.g., soy sauce) easily and provide the same inexpensively.